U.S. patent application number 10/768989 was filed with the patent office on 2005-01-06 for inter-vehicle communication apparatus.
Invention is credited to Abe, Koichi, Nishiga, Kazuya.
Application Number | 20050003844 10/768989 |
Document ID | / |
Family ID | 32954514 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050003844 |
Kind Code |
A1 |
Nishiga, Kazuya ; et
al. |
January 6, 2005 |
Inter-vehicle communication apparatus
Abstract
When a network is formed among vehicles with the use of
inter-vehicle communication units, a network-forming-request-source
vehicle sends its position serving as a reference position, its
moving direction, and requested information to surrounding vehicles
by the use of a free ID. Among the surrounding vehicles, vehicles
which are to subscribe to the network receive the position, the
moving direction, and the requested information, determine where
the vehicles are positioned among positions specified in advance
relative to the reference position, and respond at a timing
corresponding to their positions by the use of free IDs. The
network-forming-request-source vehicle receives the responses,
stops receiving responses when the number of responded vehicles
reaches an appropriate number of vehicles, and sends its genuine ID
and a vehicle communication order. Then, a restriction, such as a
restriction based on the number of times relay processes are
allowed, a restriction based on a predetermined-distance area from
the center of balance or the center, or a restriction based on a
communication period equal to a predetermined time or shorter from
when the network is formed, all of which correspond to the type of
network, is applied to form an appropriate-area network.
Inventors: |
Nishiga, Kazuya;
(Iwaki-city, JP) ; Abe, Koichi; (Iwaki-city,
JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
32954514 |
Appl. No.: |
10/768989 |
Filed: |
January 30, 2004 |
Current U.S.
Class: |
455/517 |
Current CPC
Class: |
H04W 4/02 20130101; H04W
84/18 20130101; H04W 84/02 20130101; H04W 4/029 20180201; H04W
48/04 20130101; H04W 8/005 20130101; H04W 40/248 20130101 |
Class at
Publication: |
455/517 |
International
Class: |
H04Q 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2003 |
JP |
2003-026547 |
Claims
What is claimed is:
1. An inter-vehicle communication apparatus, comprising: an
inter-vehicle communication unit; a network-forming processing
section for forming a network with surrounding vehicles; and an
information-exchange processing section for performing
information-exchange processing between network-forming vehicles,
wherein the network-forming processing section comprises a
network-forming restriction section for restricting a
network-forming area.
2. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section is a
first-order-network restriction section for restricting the forming
of a first-order network in which the inter-vehicle communication
unit directly performs communications.
3. An inter-vehicle communication apparatus according to claim 2,
wherein the first-order-network restriction section sends at least
a signal indicating the position of the vehicle to which the
inter-vehicle communication apparatus is mounted, the position
serving as a reference position, and a network-forming-request
signal to surrounding vehicles by the use of a tentative PN code
known to other vehicles, and surrounding vehicles which receive
both of the signals sequentially communicate with a
network-forming-request-source vehicle at a timing specified in
advance according to the positions of the surrounding vehicles
relative to the reference position.
4. An inter-vehicle communication apparatus according to claim 3,
wherein the first-order-network restriction section counts the
number of vehicles by signals sequentially sent from the
surrounding vehicles to the network-forming-request-source vehicle
and stops receiving when the number of vehicles is equal to or
larger than a predetermined value to restrict the forming of the
first-order network.
5. An inter-vehicle communication apparatus according to claim 3,
wherein the surrounding vehicles sequentially communicate with the
network-forming-request-source vehicle by the use of a free ID.
6. An inter-vehicle communication apparatus according to claim 5,
wherein the surrounding vehicles exchange genuine-ID data with the
network-forming-request-source vehicle after the forming of the
first-order network is restricted.
7. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section comprises a relay
section for receiving a signal from another vehicle and for sending
it to yet another vehicle.
8. An inter-vehicle communication apparatus according to claim 7,
wherein the network-forming restriction section restricts the
number of times relay processes are performed by relay sections
between when a vehicle sends information and when the
network-forming-request-source vehicle receives the
information.
9. An inter-vehicle communication apparatus according to claim 7,
wherein the network-forming restriction section restricts the
network-forming area by making, in a relaying vehicle which
receives a restriction signal from an information-requesting
vehicle, the relay section not relay a signal.
10. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section restricts the
network-forming area according to a distance from a specific
position.
11. An inter-vehicle communication apparatus according to claim 10,
wherein the specific position is one of the center of balance or
the center obtained from the network to be formed, or the position
of the vehicle to which the inter-vehicle communication apparatus
is mounted.
12. An inter-vehicle communication apparatus according to claim 10,
wherein the distance from the specific position is set according to
the number of vehicles included in the network to be formed.
13. An inter-vehicle communication apparatus according to claim 10,
wherein the specific position is a specific intersection.
14. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section restricts the
network-forming area according to the time period which has elapsed
from when information was requested.
15. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section restricts the
network-forming area according to the type of information to be
exchanged between network-forming vehicles.
16. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section comprises a storage
section for storing in advance at least one restriction value.
17. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section restricts the
network-forming area by making the inter-vehicle communication unit
of the vehicle to which the inter-vehicle communication unit is
mounted restrict processing for receiving information sent to the
vehicle.
18. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section restricts the
network-forming area by making an information-transmitting vehicle
which has received a restriction signal from an
information-requesting vehicle not perform information-transmitting
processing.
19. An inter-vehicle communication apparatus according to claim 1,
wherein the network-forming restriction section updates vehicles
positioned in a network-forming restriction area in response to
vehicle movement or the passage of time.
20. An inter-vehicle communication system, comprising: an
inter-vehicle communication apparatus located in each of a
plurality of vehicles, said apparatus comprising: an inter-vehicle
communication unit for transmitting and receiving information
between vehicles; and a network-forming processing section for
forming a network among at least some of said plurality of vehicles
and restricting the size of the network based on at least one of a
predetermined number of vehicles permitted in the network, a
predetermined number of times a relay process can be performed
between a vehicle transmitting information and another vehicle
receiving information in the network, a distance of a vehicle from
a specific position, and a predetermined time which has
elapsed.
21. A method of operating an inter-vehicle communication system,
comprising: providing an inter-vehicle communication apparatus
located in each of a plurality of vehicles, said apparatus
including an inter-vehicle communication unit for transmitting and
receiving information between vehicles; and forming a network among
at least some of said plurality of vehicles and restricting the
size of the network based on at least one of a predetermined number
of vehicles permitted in the network, a predetermined number of
times a relay process can be performed between a vehicle
transmitting information and another vehicle receiving information
in the network, a distance of a vehicle from a specific position,
and a predetermined time which has elapsed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to inter-vehicle communication
apparatuses capable of restricting an inter-vehicle network through
which information is exchanged and used among vehicles, with the
use of a communication unit mounted on each vehicle, so as not to
extend very wide.
[0003] 2. Description of the Related Art
[0004] In recent years, navigation apparatuses have been widely
mounted in vehicles, and the navigation apparatuses have been
provided with various useful functions. In addition to providing
guidance to a destination in the conventional manner, the
navigation apparatuses can display information of surrounding
facilities, and information of traffic congestion on roads with the
use of VICS, and can also automatically provide a detour if a
traffic jam occurs on a road.
[0005] Since portable telephones have been widely used, various
types of information can be obtained in vehicles from the outside.
Especially, navigation apparatuses can display necessary data on
their screens when they are connected to portable telephones to
directly communicate with an information center, or to connect to
the Internet to connect to the information center, or to various
information-providing sections to receive and use the necessary
data.
[0006] Further, with the development of communication technologies,
communication can be performed between units to exchange data at a
frequency band which can be used without a special permission, such
as a communication band having a frequency of 2.4 GHz to 2.5 GHz.
This is attractive as a means for exchanging data without
connecting units by a cable.
[0007] When a navigation apparatus is provided with such a
communication function, various units mounted in the vehicle, such
as a portable telephone, and a program set in advance can be
automatically used for communication in a desired manner. In this
case, the navigation apparatus can display various types of
information sent from the various units on the screen.
[0008] When units which can perform communication by the use of a
frequency band which can be used without any permission are used in
vehicles, communication can be achieved between the units in the
vehicles in the same manner as when communication is achieved
between a portable telephone and a navigation apparatus. In
addition, if an inter-vehicle communication unit is further
provided, mutual communication is allowed between the vehicle and
another vehicle having a compatible inter-vehicle communication
unit and located in the vicinity of the vehicle.
[0009] With the use of a program set in advance, mutual
communication can be performed automatically under a predetermined
condition. When a communication frequency band such as that
described above is used, a vehicle having an inter-vehicle
communication unit can comminute with other vehicles within a range
of about 100 meters from the vehicle in a desired manner free of
charge according to a use rule in the frequency band. In this case,
depending on program settings, the vehicle can automatically
receive predetermined information under a predetermined condition
from a vehicle located in the vicinity of the vehicle and having a
similar inter-vehicle communication unit, use it, if necessary, and
automatically send it to other vehicles.
[0010] When such an inter-vehicle automatic communication system is
used, a moving vehicle A1 can communicate with other vehicles in a
range of about 100 meters from the moving vehicle to collect or
exchange various types of information and data, as shown, for
example, by an "inter-vehicle communication local network" in FIG.
14. In addition, when a camera is mounted in the vehicle and the
camera continuously captures images ahead of the vehicle, other
vehicles can take and use the images, if necessary. The
inter-vehicle communication network can be used in various
ways.
[0011] Since the specification of such an inter-vehicle
communication local network has not been determined, it can be used
in various ways. When a user having the inter-vehicle communication
unit wants to subscribe to the network, for example, it is assumed
in one case that the user starts operating the inter-vehicle
communication unit to prepare for sending the position and the
moving direction of the vehicle, the inter-vehicle communication
ID, and other information, and, when the network connection is
established, enters a basic-information network for exchanging
basic information.
[0012] Various other optional networks can be prepared in advance,
such as a same-driving-path network which includes vehicles moving
along the same driving path in the same direction as the local
vehicle and vehicles which seem to directly relate to the movement
of the local vehicle, and further, a traffic-jam-information
network for providing information used in various situations when a
traffic jam occurs in the same driving path. In the traffic-jam
information network, detour information useful in avoiding the
traffic jam can be exchanged. The traffic-jam information network
may be one of multiple optional sub-networks in the
same-driving-path network, or may be formed as an independent
optional network.
[0013] When the user wants to subscribe to such an optional
network, the user performs an input for network subscription. When
the local vehicle has a navigation apparatus and is moving toward
the destination, the inter-vehicle communication unit searches for
vehicles which have operating inter-vehicle communication units in
a range where communications are possible, and which move in the
same driving path in the same direction as the local vehicle, or
are likely to come to the same driving path, and displays them on a
screen. Alternatively, the local vehicle automatically sends and
receives necessary information to and from the vehicles.
[0014] Further various optional networks can be considered, such as
a vehicle-group network which includes vehicles having their
vehicle IDs registered in advance, and a surrounding-vehicle
network which includes all vehicles located around an intersection
and which can be used for all vehicles to pass through the
intersection safely. These networks are prepared in advance, and if
necessary, such networks can be formed in a desired manner. Since
other vehicles also form networks, the user can perform settings
according to a setting guidance displayed on the screen before
movement or during movement to determine a network to which the
vehicle is to subscribe. Therefore, vehicles automatically form
optional networks at a predetermined timing.
[0015] When the user wants to subscribe to a particular network,
the user performs an input for network subscription. As for
information specified in advance so as to be used in the network,
the information of the user's vehicle is open to all network users,
and the user can use the information of the other vehicles in the
network in a desired way.
[0016] As shown in FIG. 14, a vehicle A4 is in a first-order
inter-vehicle communication local network (A1) for the local
vehicle A1, the network (A1) existing in a predetermined-distance
range where communications are possible around the local vehicle
A1, and the local vehicle A1 is in an inter-vehicle communication
local network (A4) for the vehicle A4 where the vehicle A4 can
perform communications. Therefore, the local vehicle A1 and the
vehicle A4 can communicate with each other. Further, the vehicle A4
is in an inter-vehicle communication local network (A6) for a
vehicle A6, and the vehicle A6 is in the inter-vehicle
communication local network (A4), which is a second-order local
network for the local vehicle. Therefore, the vehicle A4 and the
vehicle A6 can communicate with each other.
[0017] Furthermore, in FIG. 14, through an inter-vehicle
communication local network (A6) for the vehicle A6, the vehicle A6
can communicate with a dealer D3 having the same communication unit
as the inter-vehicle communication unit. The inter-vehicle
communication local network (A6) is a third-order local network for
the local vehicle. The dealer 3 forms an independent information
transfer system together with dealers D1 and D2 which are in the
same group as the dealer 3, and the independent information
transfer system includes an information center. Therefore, the
vehicle A6 can take various types of information from the
information center, and can also use a statistical data base in the
information center to obtain a correctly guided path based on the
latest traffic information.
[0018] With this, the vehicle A4, which is connected to the vehicle
A6 through the inter-vehicle communication local networks (A6 and
A4), can use the information and data which the vehicle has
received from the information center. In addition, the local
vehicle A1, which is connected to the vehicle A4 through the
inter-vehicle communication local networks (A4 and A1), can use the
information and data which the vehicle has received from the
information center by the information transfer system, through the
vehicle A4, which forms the second-order local network for the
local vehicle. By the information transfer system, the local
vehicle A1 can directly access the information center to obtain
information.
[0019] In the case shown in FIG. 14, the information center is
connected to the World Wide Web (WWW) on the Internet, and can
obtain information through the Internet, if necessary. The Internet
users can use the information of the information center. The
Internet can be used in vehicles through a portable telephone
carried therein, and received information can be displayed on a
screen. Therefore, the information of the information center can
also be obtained through the Internet.
[0020] The local vehicle can obtain various types of information
through various networks, and in addition, can automatically obtain
information which each vehicle possesses and allows to be made open
to the public, by searching. For example, the local vehicle can
obtain detailed map data which includes narrow roads, possessed by
a particular vehicle to use for route calculations. The local
vehicle can also use facility information and resort information
collected independently, in the same way as various web sites on
the Internet.
[0021] As described above, with the use of an inter-vehicle
communication unit mounted in each vehicle, the inter-vehicle
communication local network of the local vehicle can be connected
through the inter-vehicle communication local network of another
vehicle which is in the inter-vehicle communication local network
of the local vehicle, to still another inter-vehicle communication
local network. If a vehicle therein can obtain information from an
independent information transfer system, for example, the local
vehicle can also use the information.
[0022] Further, when one of the networks has an information center
therein, the local vehicle can use information and data thereof.
When any of the networks can be connected to the Internet, the
local vehicle can obtain information on the Internet. Inter-vehicle
communication networks form a very broad network in this way, and
it is expected that the inter-vehicle communication networks will
be further developed and used in various manners, including mutual
use of images captured by cameras mounted to vehicles.
[0023] When inter-vehicle communication networks such as those
described above are used, for example, to form the
same-driving-path network among vehicles moving along the same path
in the same direction, or to form a traffic-jam network through
which predetermined information is mutually transmitted and
received when a traffic jam occurs, or when a traffic-jam network
serving as a single network is used, the network is formed in a way
shown in FIG. 15.
[0024] In the case shown in FIG. 15, the local vehicle L3 is moving
along a guided path indicated by a driving path G. When the local
vehicle L3 indicated by the local vehicle position mark is moving
along a road U1, it can form a local network (L3), indicated by a
circular communication area, for the local vehicle L3 by a mounted
inter-vehicle communication unit.
[0025] In the case shown in FIG. 15, the local network (L3) for the
local vehicle L3 can physically include a total of seven vehicles,
the local vehicle L3, a vehicle L2 moving along the same driving
path G and located behind the local vehicle L3, a vehicle L4 moving
along the same driving path G and located in front of the local
vehicle L3, a vehicle L5 moving along the same driving path G and
located beyond an intersection C2 positioned before the vehicle L4,
a vehicle R3 moving along the road U1 but in the opposite
direction, a vehicle S2 moving from the right in the figure to an
intersection C2 along a road W1 intersecting with the road U1,
along which the local vehicle L3 is moving, at the intersection C2,
and a vehicle S3 moving from the left in the figure to the
intersection C2 along the road W1.
[0026] When surrounding-vehicle networks are formed around the
local vehicle L3, the local vehicle L3 can communicate with
vehicles which cannot be seen from the local vehicle L3, and can
obtain, for example, camera images therefrom. A person who is
likely to suddenly rush out in front of the local vehicle L3 from a
place which cannot be seen from the local vehicle because of a
building can be observed from the camera images of those vehicles,
and some measure can be taken in advance. A plurality of camera
images taken at the intersection immediately before the local
vehicle can be displayed on a screen in parallel to allow the
driver to see the images captured from all directions at the
intersection. Therefore, the driver and other passengers can travel
in the local vehicle with relief even at intersections where
accidents occur frequently.
[0027] In the case shown in FIG. 15, the vehicle L4 moving in front
of the local vehicle L3 is not provided with an inter-vehicle
communication unit used for forming an inter-vehicle network, or it
is not using the communication unit (by turning it off, for
example) even if the unit is provided. Therefore, this vehicle is
not included in any network. Vehicles moving in the direction
opposite to the direction in which the local vehicle L3 is moving
are not shown in FIG. 15 so as not to make the figure more
complicated. For example, one of such vehicles, the vehicle R3, can
be included in the inter-vehicle communication network of the local
vehicle L3. When it is determined that information sent from the
vehicle R3 is rarely used, the vehicle R3 can be set in advance as
a vehicle excluded from the network in the same-driving-path
network or the traffic-jam network of the local vehicle L3 to
automatically exclude the vehicle R3. The vehicle R3 can be
included in a drive network for exchanging surrounding-facility
information among vehicles surrounding the local vehicle L3.
[0028] The local network (L3) of the local vehicle L3 is connected
to the local network (L5) of the vehicle L5 moving in front of the
local vehicle L3 in the same driving path G. Since the local
vehicle L3 is within the local network (L5) of the vehicle L5, the
local vehicle L3 and the vehicle L5 can transmit and receive
information and data to and from each other. In the local network
(L5) of the vehicle L5, a vehicle L7 moving in front of a vehicle
L6 which is moving in front of the vehicle L5 has a local network
(L7). The vehicles L5 and L7 can transmit and receive information
and data to and from each other in the same way.
[0029] A vehicle L8 moving in front of the vehicle L7 in the same
road past an intersection C3, a vehicle L9 located on a bridge B1
in front of the vehicle L8, and a vehicle L10 moving in front of
the vehicle L9 but not reaching an intersection C4 are moving and
form respective local networks, and can transmit and receive
information and data to and from each other. With this, the local
vehicle L3 can obtain the information from the vehicle L10 through
the local networks L10, L9, L7, and L3. Therefore, when the local
vehicle is going to pass through a certain intersection but does
not have detailed map data thereof, the local vehicle can send a
request for the map data, search vehicles connected through local
networks for a vehicle having the map data, and use it.
[0030] When the vehicle L10 has a camera, for example, the local
vehicle L3 can obtain images taken by the camera. This means that
the congestion or traffic-jam condition of a road can be actually
seen on a screen by the use of a camera provided on a vehicle
moving far ahead of the local vehicle. Since similar local networks
are also formed to the rear of the local vehicle, similar
information and the information of the local vehicle can be
automatically transferred to vehicles connected to the networks and
moving to the rear of the local vehicle. With the use of such
camera images, a real bird's eye view can be implemented, in which
far-away scenery can be seen. Further, fixed-point observation is
also possible in a way in which a specific intersection such as an
intersection where the local vehicle is going to turn right is
selected, vehicles moving near the intersection are automatically
selected, and the camera images of the vehicles are sequentially
switched to always display camera images related to the
intersection.
[0031] When the local vehicle is going to pass through an
intersection C2 where a traffic signal is not provided, for
example, a vehicle S2 moving from the right in the figure to the
intersection and having a local network (S2) can be checked on the
screen of the local vehicle by a vehicle mark or other icon, so
that the driver can drive through the intersection at a low speed
while paying attention. In this way, the state of a vehicle located
at a place which cannot be seen can be understood in advance to
avoid any dangerous situations during driving.
[0032] Such information transfer is possible between four or more
wheeled vehicles. In addition, it is also possible between
two-wheeled vehicles. When communication units are made compact,
pedestrians can carry them. Then, the driver can see a person who
may rush out in front of the local vehicle from a place which is
out of view, on the screen, to drive the local vehicle safely while
paying attention to the person. When pedestrians have such portable
communication units for forming local networks, various types of
information can be used by using local networks between vehicles
such as those described above. Then, in addition to the local
networks between vehicles, local networks can be also formed
between carried mobile units to allow similar information to be
transferred.
[0033] When a vehicle S3 is going to turn left at the intersection
C2 where a traffic signal is not provided along the road Ul which
is now congested, for example, it is possible for the driver of the
vehicle S3 to perform actual conversation with the driver of the
local vehicle or to send a predetermined signal to the driver of
the local vehicle to exchange a request for waiting for a moment
from the driver of the vehicle S3 and an affirmative response from
the driver of the local vehicle, so that the vehicle S3 can turn
left immediately. If the local vehicle were the vehicle S3, the
driver of the local vehicle can communicate with the drivers of
other vehicles moving along the congested road, so that the local
vehicle can turn left smoothly at the intersection having no
traffic signal. In the same way, a vehicle can smoothly go into a
congested expressway from another road by performing the same
communication.
[0034] Furthermore, by using the statistical data of information
such as that shown in FIG. 14 through the information collection
function of another vehicle which can be connected to a local
network which includes the information center, various types of
information can be obtained, such as specific-road traffic-jam
information for certain weather or season, traffic-restriction
information when it is snowing, traffic-restriction information
when events such as a festival are held, and information of byroads
which can be used in a traffic jam or congestion and which are
known only to local people. Safe driving is made possible without
any wasted time. As for byroads known only to local people, when
the driving-path track data of each vehicle is obtained in the
same-driving-path network, if a local person uses a byroad in the
network, the data of the byroad can be automatically searched for
and obtained to share the data.
[0035] Japanese Unexamined Patent Application Publication No.
2001-273593 discloses a technology in which communications are
performed between an emergency vehicle and general vehicles through
a base station to report to the general vehicles that the emergency
vehicle is approaching. Japanese Unexamined Patent Application
Publication No. Hei-9-7096 discloses a technology in which an
emergency vehicle sends a radio signal having a predetermined
frequency and general vehicles receive the signal to know that the
emergency vehicle is approaching. Japanese Unexamined Patent
Application Publications No. Hei-10-153436, No. Hei-10-311730, and
No. 2000-20889 disclose technologies in which traffic information
is received from the outside.
[0036] In an inter-vehicle information network system such as that
described above, when a car accident occurs ahead of the local
vehicle on the road on which the local vehicle is current moving
and the road is blocked, the accident information can be
sequentially transmitted from the vehicle which caused the accident
or a vehicle which was moving thereafter to the following
vehicles.
[0037] When such an accident occurs, conventionally, the accident
information is collected at a traffic information center, the
information is confirmed, and then it is distributed through VICS
or broadcasting to an area related to the accident. Therefore, the
information is transferred to vehicles moving after the car which
caused the accident, but not until some time elapses after the
accident occurred.
[0038] In contrast, in an inter-vehicle information network system
such as that described above, the accident information is
transmitted immediately to the following vehicles which will be
most affected by the accident.
[0039] Even when it is found that the road is blocked by a car
accident or other problem, a correct detour to avoid the accident
cannot be obtained immediately in vehicles provided with navigation
apparatuses using older data, or vehicles provided with navigation
apparatuses having a very low calculation speed. Not all vehicles
have highly functional navigation apparatuses, which can
immediately provide a correct detour for driving. There are many
drivers who want to use detour data provided by highly functional
navigation apparatuses. Since local people frequently have detailed
or special local road information, detours which the local people
select are appropriate in many cases. Therefore, it is preferred
that the data of such detours be obtained.
[0040] When a road is blocked by a car accident, even if detour
information is transferred from a vehicle having a highly
functional navigation apparatus, the detour is not necessarily
appropriate for all following vehicles. The detour is most
appropriate for that vehicle, but there may be another appropriate
detour for the following vehicles.
[0041] In the case shown in FIG. 15, when a vehicle L9 causes a car
accident on the bridge B1 to block the bridge B1, a vehicle L7 can
search for a detour in which the vehicle L7 turns right at an
intersection C3 to move on a road W2, turns left at an intersection
C11, passes through a bridge B3, turns left at an intersection C12
to move on a road W3, and turns right at an intersection C4 to
return to the driving path G, along which the vehicle L7 was to
move. Therefore, when this information is sent to the following
vehicle L5, the vehicle L5 can take this appropriate detour based
on the information.
[0042] The detour information can be sent to and used by the
further following local vehicle L3 and the following vehicle L2. In
this case, however, the local vehicle L3 can search, by its
navigation apparatus, for a detour in which the local vehicle L3
turns left at the intersection C2 to move on the road W1, turns
right at an intersection C6, passes through an intersection C7 and
a bridge B2, turns right at an intersection C8 to move on a road
W3, and turns left at the intersection C4 to return to the driving
path G, along which the local vehicle L3 was to move. This detour
is shorter than the detour which the vehicle L7 searched for, and
hence more appropriate for the local vehicle L3. The following
vehicle L2 can use this detour information of the local vehicle
L3.
[0043] In the same way, a vehicle L1 can use the above-described
two pieces of detour information, but can search for a more
appropriate detour in which the vehicle L1 turns left at an
intersection C1, turns right at an intersection C5, and moves
through the detour which the local vehicle L3 found, to immediately
avoid the road where the traffic jam occurred. Therefore, the
vehicle L1 can immediately move through the detour. This
information can be transferred to all vehicles connected through
the local networks, but it is meaningless for the vehicle L7, and
it is not useful for the local vehicle L3 because it is not
appropriate in many cases for the local vehicle L3 to make a U-turn
to go back to the intersection C1, and turn right to take the
detour which the vehicle L1 found.
[0044] In this way, even when local networks can be connected to
form a wide network, a network having a restricted area may be
preferable depending on the information to be obtained. It is
preferred in many cases that the size of a network be restricted
for shopping information at nearby stores and neighborhood-event
information, in addition to detour information used in the event of
a car accident or traffic jam.
[0045] To restrict the size of a network, coordinates or road links
can, for example, be used, but are not preferable for networks in
which network components, such as vehicles, move to change the
locations of the networks, because a huge amount of calculation is
required.
[0046] In addition to an area restriction, such as that applied to
an area around the local vehicle, a time restriction, such as that
used when the information of events to be held by ten o'clock in
the morning of that day is obtained, may be required for a specific
network. In such a case, coordinates or road links cannot be used
for restriction.
[0047] When the user wants to know a detour around a car accident
or traffic jam, or when the user wants to form a detour-information
network with vehicles surrounding the local vehicle, if the user
requests the surrounding vehicles to exchange IDs for forming the
network, the surrounding vehicles may respond at a similar time. If
there are many surrounding vehicles, the responses therefrom may
cause interference, which disables correct receiving and hence
disables forming a network. If PN code and IDs are known in
advance, a transmission sequence can be determined in advance to
avoid the interference. If PN code and IDs are not known, an
appropriate action cannot be taken.
[0048] After a network forming request is sent to surrounding
vehicles, when it is found that there are many vehicles which can
respond to the request in the area of the first-order local network
in which direct communications with the local vehicle is possible,
if forming a network with too many vehicles is not a good idea, the
number of vehicles to be included in the first-order local network
may be restricted. To this end, means for reducing the number of
vehicles which respond at a time to an appropriate number is
necessary.
[0049] Information exchanges are impossible if PN code and IDs are
not known to each other in forming a network. It is not preferred
that the PN code and ID of the local vehicle be sent to all
surrounding vehicles. Especially when the number of vehicles is to
be restricted in the area where direct communications with the
local vehicle is possible, it is not necessary to inform all
surrounding vehicles of the PN code and ID of the local vehicle.
Means for handling this issue is required.
SUMMARY OF THE INVENTION
[0050] Accordingly, it is an object of the present invention to
provide an inter-vehicle communication apparatus which can easily
apply an appropriate restriction to a network formed between
vehicles by the use of inter-vehicle communication units for
information exchanges, which does not cause interference when the
network is formed, and which can prevent PN code and IDs from being
conveyed superfluously.
[0051] The foregoing object is achieved in one aspect of the
present invention through the provision of an inter-vehicle
communication apparatus, including an inter-vehicle communication
unit, a network-forming processing section for forming a network
with surrounding vehicles, and an information-exchange processing
section for performing information-exchange processing between
network-forming vehicles, wherein the network-forming processing
section includes a network-forming restriction section for
restricting a network-forming area. When a network is formed among
vehicles by the use of inter-vehicle communication units for
information exchanges, various network-forming restriction sections
can apply appropriate restrictions, which prevents an
information-requesting vehicle from receiving meaningless
information generated in a too-wide network.
[0052] The network-forming restriction section may be a
first-order-network restriction section for restricting the forming
of a first-order network in which the inter-vehicle communication
unit directly performs communications. Vehicles positioned in an
area where the inter-vehicle communication unit can communicate can
be restricted to an appropriate number of vehicles for
communication, which especially prevents interference caused when
the network is formed.
[0053] The inter-vehicle communication apparatus may be configured
such that the first-order-network restriction section sends at
least a signal indicating the position of the vehicle to which the
inter-vehicle communication apparatus is mounted, the position
serving as a reference position, and a network-forming-request
signal to surrounding vehicles by the use of a tentative PN code
known to other vehicles, and surrounding vehicles which receive
both of the signals sequentially communicate with a
network-forming-request-source vehicle at a timing specified in
advance according to the positions of the surrounding vehicles
relative to the reference position. In this case, the PN code is
prevented from being superfluously made open to the public, and a
network-forming signal can be transmitted and received easily,
always preventing interference.
[0054] The first-order-network restriction section may count the
number of vehicles by signals sequentially sent from the
surrounding vehicles to the network-forming-request-source vehicle
and stop receiving when the number of vehicles is equal to or
larger than a predetermined value to restrict the forming of the
first-order network. In this case, the
network-forming-request-source vehicle can always apply an
appropriate restriction to vehicles which perform information
exchanges in the first-order network.
[0055] The surrounding vehicles may sequentially communicate with
the network-forming-request-source vehicle by the use of a free ID.
Alternatively, the surrounding vehicles may exchange genuine-ID
data with the network-forming-request-source vehicle after the
forming of the first-order network is restricted. In either case,
the genuine ID is always prevented from being superfluously made
open to the public.
[0056] The network-forming restriction section may include a relay
section for receiving a signal from another vehicle and for sending
it to yet another vehicle. In this case, the inter-vehicle network
can be extended widely. Sightseeing information or resort
information, for example, can be obtained from vehicles located in
a wide area, and the most appropriate information can be selected
among many pieces of information.
[0057] The network-forming restriction section may restrict the
number of times relay processes are performed by relay sections
between when a vehicle sends information and when the
network-forming-request-source vehicle receives the information. In
this case, even when the network has a very wide area due to the
provision of the relay section, the size of the network is always
and easily restricted to a predetermined area.
[0058] The network-forming restriction section may restrict the
network-forming area according to a distance from a specific
position. The specific position may be the center of balance or the
center obtained from the network to be formed, or the position of
the vehicle to which the inter-vehicle communication apparatus is
mounted. In any case, the network is always and easily restricted.
Especially when desired information tends to depend on a distance,
the network can be appropriately restricted.
[0059] The distance from the specific position may be set according
to the number of vehicles included in the network to be formed.
When the network is restricted according to the number of times
relay processes are allowed, or according to a distance, the number
of vehicles included in the network may become very large or very
small. This is prevented when the network is restricted according
to the number of vehicles included in the network.
[0060] The specific position may be a specific intersection.
[0061] The network-forming restriction section may restrict the
network-forming area according to the time period which has elapsed
from when information was requested. In this case, when time is
important as in information of an event to be held at a specific
time, receiving information which becomes meaningless because the
corresponding time has passed is not performed.
[0062] The network-forming restriction section may restrict the
network-forming area according to the type of information to be
exchanged between network-forming vehicles. In this case, an
appropriate network-forming area is specified according to the
special nature of the information, such as detour information,
traffic-jam information, or sightseeing-guide information.
[0063] The network-forming restriction section may include a
storage section for storing in advance a restriction value. In this
case, the network is appropriately restricted easily and quickly,
and the user does not need to enter a restriction.
[0064] The network-forming restriction section may restrict the
network-forming area by making the inter-vehicle communication unit
of the vehicle to which the inter-vehicle communication unit is
mounted restrict processing for receiving information sent to the
vehicle. In this case, network forming is always restricted without
depending on other vehicles.
[0065] The network-forming restriction section may restrict the
network-forming area by making, in a relaying vehicle which
receives a restriction signal from an information-requesting
vehicle, the relay section not relay a signal. In this case, the
vehicle to which the inter-vehicle communication apparatus is
mounted does not need to perform network-forming restriction
processing such as those described above, and the restriction
processing is achieved in the processing of the relay section of
another vehicle.
[0066] The network-forming restriction section restricts the
network-forming area by making an information-transmitting vehicle
which has received a restriction signal from an
information-requesting vehicle not perform information-transmitting
processing. The information-requesting vehicle achieves the
network-forming restriction processing. Each vehicle does not need
to perform relay processing, and the information-requesting vehicle
reduces a processing load.
[0067] The network-forming restriction section may update vehicles
positioned in a network-forming restriction area in response to
vehicle movement or elapsed time. In this case, an appropriate
network is always formed in response to a change in the structure
of the network, caused by vehicle movement or elapsed time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] FIG. 1 is a functional block diagram of an inter-vehicle
communication apparatus according to an embodiment of the present
invention, showing the main functions and the relationship
therebetween.
[0069] FIG. 2 is a flowchart showing the overall operation in the
embodiment.
[0070] FIG. 3 is a flowchart of network-forming processing in
surrounding vehicles in response to a network-forming request,
which is performed in step S2 of FIG. 2.
[0071] FIG. 4 is a flowchart of first-order-network size
restriction processing and processing for deciding vehicles to be
included in the first-order network, in the
network-forming-request-source vehicle, performed in step S3 of
FIG. 2.
[0072] FIG. 5 is a flowchart of network-forming-restriction
decision processing performed in step S6 of FIG. 2.
[0073] FIG. 6 is a flowchart of network-forming restriction
processing based on the number of times relay processes are
allowed, performed in step S32 of FIG. 5.
[0074] FIG. 7 is a flowchart of network-forming restriction
processing based on a predetermined-distance area, performed in
step S34 of FIG. 5.
[0075] FIG. 8 is a flowchart of network-forming restriction
processing based on a network-forming time period, performed in
step S36 of FIG. 5.
[0076] FIG. 9 is a timing chart showing operations in
first-order-network-size restriction processing performed together
with surrounding vehicles.
[0077] FIG. 10 illustrates an example order assignment to vehicles
around a network-forming-request-source vehicle in the
first-order-network-size restriction processing.
[0078] FIG. 11 illustrates an example network-forming restriction
based on the number of times relay processes are allowed.
[0079] FIG. 12 illustrates an example network-forming restriction
based on a predetermined-distance area.
[0080] FIG. 13 illustrates an example network-forming restriction
based on a network-forming time period.
[0081] FIG. 14 illustrates aspects of forming inter-vehicle
networks.
[0082] FIG. 15 illustrates a driving-path network formed of
inter-vehicle networks.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0083] Embodiments of the present invention will be described below
by referring to the drawings. FIG. 1 is a block diagram of
functional sections and their arrangement used for solving the
above-described problems in an inter-vehicle communication
apparatus according to the present invention. The functional
sections can be operated according to operation flows shown in FIG.
2 to FIG. 8. The inter-vehicle communication apparatus 1 is
provided with a system control section 2 having a CPU, a ROM for
storing software which includes a program for controlling each
functional section of the inter-vehicle communication apparatus, a
RAM for temporarily storing data, and other components as is known.
The system control section 2 is connected to a navigation apparatus
3, and the signals of a moving-direction detection section 31 and a
local vehicle-position detection section 32 provided for the
navigation apparatus 3 can be used in the inter-vehicle
communication apparatus. Each functional section shown in FIG. 1
can be called a means for performing each function.
[0084] The inter-vehicle communication apparatus 1 basically
includes a network-forming-request processing section 4 for mainly
performing operations when the local vehicle wants to form a
network, a network-forming-response processing section 5 for
performing operations in order to respond to a network-forming
request sent from another vehicle, a
network-forming-restriction-decision processing section 6 for
restricting the network to have an appropriate area when a request
for forming the network is issued, an information-exchange
processing section 7 for exchanging desired information after the
network is formed, a relay-control processing section 8 for
relaying information sent from a vehicle included in the
first-order network of the local vehicle to other vehicles included
in the first-order network, or to other vehicles included in the
second-order, third-order, etc., networks connected to the
first-order network, and an inter-vehicle communication unit 9 for
communicating with other vehicles.
[0085] The network-forming-request processing section 4 is provided
with a first-order-network restriction section 41 for restricting
vehicles included in the first-order network serving as a local
network for direct communications with the local vehicle; a
responded-vehicle-count monitoring section 42 for monitoring the
number of vehicles which have responded to a network forming
request sent from the local vehicle, in order to perform a
restriction in the first-order-network restriction section 41; a
first-order-network-forming-vehicle decision section 43 for
deciding vehicles to be finally included in the first-order
network; an ID output section 44 for outputting IDs required for
communications; and a PN-code output section 47 for outputting a PN
code required for communications.
[0086] The ID output section 44 includes a free-ID output section
45 for outputting a free ID which is determined in advance and
which can be immediately recognized by other vehicles in an initial
stage of network forming, and a genuine-ID output section 46 for
outputting a genuine ID required for information-exchange
communications with vehicles included in the first-order network
after the vehicles are included in the first-order network. In the
same manner as the ID output section 44, the PN-code output section
47 includes a tentative-PN-code output section 48 for outputting a
tentative PN code used by other vehicles, and a genuine-PN-code
output section 49 for outputting a genuine PN code used for
information-exchange communications with vehicles included in the
first-order network after the vehicles are included in the
first-order network.
[0087] The network-forming-response processing section 5 is
provided with a network-forming determination section 51 for
determining when a network-forming request for specific-information
exchanges is sent from another vehicle, whether the local vehicle
subscribes to the network; a network-forming-request-vehicle
reference-position and moving-direction detection section 52 for
detecting, when the network-forming determination section 51 has
determined that the local vehicle subscribes to the network, a
reference position which is the position of the vehicle which has
sent the network-forming request and the moving direction of the
vehicle in data received from the vehicle; a local vehicle-position
input section 53 for inputting the position of the local vehicle
from the navigation apparatus 3; a relative-local-vehicle-position
detection section 54 for detecting a relative position of the local
vehicle as described later from the position and the moving
direction of the network-forming-request vehicle detected by the
network-forming-request-v- ehicle reference-position and
moving-direction detection section 52; and a
network-forming-response output section 55 for reporting at a
timing determined in advance to the network-forming-request vehicle
that the local vehicle may subscribe to the network, according to
the relative position detected by the
relative-local-vehicle-position detection section 54.
[0088] The network-forming-restriction-decision processing section
6 is provided with a network-type-signal input section 61 for
inputting a signal which indicates the type of the requested
network when forming the network is requested; a
restriction-area-signal taking section 62 for receiving a signal
which specifies an appropriate network restriction area according
to the type of the network input by the network-type-signal input
section 61 or according to the user's needs; a
relay-count-restriction processing section 63 for performing
processing in which a vehicle which needs the number of relay
processes equal to or larger than a predetermined relay count is
excluded from vehicles to be included in the network, according to
the signal which indicates the restriction area received by the
restriction-area-signal taking section 62; a
network-forming-distance-area-restriction processing section 64 for
performing processing in which vehicles located outside the area
defined by a predetermined distance from a specific point such as
the center of balance or the center of the network are excluded
from vehicles to be included in the network; a
communication-time-restriction processing section 65 for performing
processing in which a vehicle which sends information when a
predetermined time or more elapses after forming the network is
requested is excluded from vehicles to be included in the network;
and a restriction-area-signal output section 66 for outputting a
restriction-area signal used by a vehicle included in the network,
not the vehicle which has requested to form the network, to apply
the same restriction as that applied in the network restriction
processing described above by controlling a process for relaying
information from another vehicle to the vehicle which has requested
to form the network.
[0089] The network-forming-restriction-decision processing section
6 can apply a restriction to vehicles included in the network as
described above, and in addition, can restrict not only the network
itself but also received signals in processing circuits. A
restriction can be substantially applied to the vehicles included
in the network by a setting such that, for example, the
relay-count-restriction processing section 63 stops performing the
internal processing of a signal received through the number of
relay processes equal to or larger than a predetermined number, the
network-forming-distance-area-restriction processing section 64
stops performing the internal processing of a received signal sent
from outside of the area a predetermined distance from a specific
point such as the center of balance or the center of the network,
or the communication-time-restriction processing section 65 stops
performing the internal processing of a signal received when a
predetermined time or more elapses after forming the network is
requested.
[0090] The network-forming-request processing section 4, the
network-forming-response processing section 5, and the
network-forming-restriction-decision processing section 6 can be
collectively regarded as a network-forming processing section for
forming a network to communicate with other vehicles in the
inter-vehicle communication apparatus.
[0091] The information-exchange processing section 7 is provided
with an information-request input section 71 for inputting the
signal of information which another vehicle requires, the signal
being output from the other vehicle to the vehicle which formed the
network after the network is formed; an information search section
72 for searching the local vehicle for the required information
received from another vehicle; an required-information output
section 73 for outputting information obtained as a result of
search to another vehicle, which has required the information; an
information-request output section 74 for outputting, when the user
of the local vehicle wants to obtain information by forming a
network, an information request to surrounding vehicles before
forming the network is decided, or an information request after
forming the network is decided; an information receiving input
section 75 for receiving information sent from another vehicle in
response to the information request sent by the local vehicle; and
an information-use processing section 76 for performing various
information-use processes, such as, when the obtained information
is detour information, sending it to the navigation apparatus
3.
[0092] The relay-control processing section 8 is provided with a
relay-signal input section 81 for inputting a relay signal for
sending information from a vehicle included in the first-order
network formed by the local vehicle to other vehicles included in
the first-order network or to vehicles included in the
second-order, third-order, etc., networks connected to the
first-order network; a relay-signal output section 82 for relaying
and outputting the relay signal to the predetermined other
vehicles; and a network-forming-restriction relay processing
section 83 for performing operations in the same way as the
network-forming-restrict- ion-decision processing section 6 so as
not to output the relay signal to the vehicle which requested the
information when a network-forming area has been restricted as
described above even if the relay signal is input.
[0093] The network-forming-restriction relay processing section 83
performs almost the same processing as the
network-forming-restriction-de- cision processing section, and
includes a network-type-signal input section 84 for inputting the
signal type of the requested information output from the
information-request output section 74 of the vehicle which requires
network forming; a restriction-area-signal input section 85 for
inputting a signal related to the area to which the network is
restricted, output from the restriction-area-signal output section
66 of the vehicle which requires network forming; a
relay-count-restriction processing section 86 for performing
restriction processing in which information for which the number of
relay processes equal to or larger than a predetermined relay count
is not relayed to the vehicle which required the information; a
network-forming-distance-area-restriction processing section 87 for
performing processing in which information sent from a vehicle
located outside the area defined by a predetermined distance from a
specific point such as the center of balance or the center of the
network is not relayed; and a communication-time-restrictio- n
processing section 88 for performing, when a communication-time
restriction is applied to the network, processing in which
information is not relayed if the communication time has already
elapsed.
[0094] In restriction decision processing in which a network-area
restriction is decided, in addition to the above-described aspect,
a restriction can be substantially applied to the network by a
process performed by the information transmission side, such as a
process in which information is not sent from the local vehicle to
a vehicle which requested the information when the number of
required relay times is equal to or larger than a predetermined
number, a process in which information is not sent from the local
vehicle to a vehicle which requested the information when the local
vehicle is located outside the area specified by the
network-forming-distance-area restriction, or a process in which
information is not sent from the local vehicle to a vehicle which
requested the information if a predetermined time has elapsed since
the information was requested. Any of the above-described various
types of network-restriction-decision processing can be performed
in parallel.
[0095] The inter-vehicle communication unit 9 is provided with a
transmission section 91 and a receiving section 92, and performs
communications in a frequency band, e.g., of 2.4 to 2.5 GHz by
using a tentative PN code which all vehicles know and free IDs in
an initial stage when the network is being formed and by using a
genuine PN code and genuine IDs after vehicles included in the
network are determined.
[0096] Then inter-vehicle communication apparatus 1 having the
above-described functional sections performs
inter-vehicle-network-formin- g processing according to a basic
operation flow shown in FIG. 2. In the case shown in FIG. 2, in the
inter-vehicle-network (NW) forming processing performed by the
inter-vehicle communication apparatus, a vehicle which requests
network forming performs an initial output process in step S1. As
shown in FIG. 2, a free ID is used, and items, such as the position
and moving direction of the local vehicle, information to be
exchanged, and a response receiving time at which the mode is
changed from an initial transmission mode in which the initial
output is repeatedly performed within a predetermined time to a
receiving mode in which signals are received from other vehicles,
are sent with the use of a tentative PN code which all vehicles
have already known. This operation is performed by the
corresponding functional sections in the network-forming-request
processing section 4 shown in FIG. 1.
[0097] Then, network-forming processing is performed in step S2 in
vehicles surrounding the vehicle which requested network forming,
in response to the network-forming request. FIG. 3 shows a more
detailed operation of the network-forming processing, described
later. Next, in step S3, the vehicle which requested network
forming performs first-order-network size restriction processing
and processing for deciding vehicles to be included in the
first-order network. FIG. 4 shows a more detailed operation
thereof, described later. Then, the vehicle which requested network
forming sends its genuine ID and a data-transmission vehicle order
to the vehicles to be included in the first-order network, which
was decided as described above, by using a genuine PN code in step
S4.
[0098] In step S5, the vehicles to be included in the first-order
network send to the vehicle which requested network forming, in the
data-transmission vehicle order, that is, at a timing corresponding
to each vehicle after the transmission start time, their genuine
IDs and the information of vehicles included in the networks which
include the vehicles, the networks being the second-order,
third-order, etc., networks (multiple-order networks) viewed from
the vehicle which requested network forming, by using the genuine
PN code. Then, restriction decision processing for the
multiple-order networks obtained this way is performed in step S6.
FIG. 5 shows the restriction decision processing in more detail,
and will be described later.
[0099] The vehicles to be included in the network are finally
decided in step S7, and information-exchange processing is
performed between vehicles in the network in step S8. Since the
local vehicle and the vehicles included in the network move and
there may be a vehicle located outside the network due to the
applied restriction, processing for handling a change in the
vehicles included in the network is performed in step S9. Then, the
inter-vehicle-network-forming processing returns to step S7 to
decide vehicles to be included in the network again, and the
subsequent processes are performed. The processing for handling a
change in the vehicles included in the network, performed in step
S9, is substantially the same as the restriction decision
processing for the multiple-order networks, performed in step
S6.
[0100] The network-forming processing performed in step S2 of FIG.
2 in vehicles surrounding the vehicle which requested network
forming, in response to the network-forming request, can be
sequentially achieved according to the operation flow shown in FIG.
3. The network-forming processing shown in FIG. 3 will be described
by referring to FIG. 9 and FIG. 10. In the case shown in FIG. 3,
the vehicles surrounding the vehicle which requested network
forming receive a signal from the vehicle which requested network
forming in step S11. The request-source vehicle sends the
network-forming request repeatedly during a period from t1 to t2
shown in FIG. 9(a), and the surrounding vehicles receive the
signal.
[0101] Then, the surrounding vehicles determine in step S12 whether
they accept the network-forming request sent from the
request-source vehicle. The surrounding vehicles examine the
information to be exchanged, sent from the vehicle which requested
network forming, and determine whether the information is related
to the vehicles or whether they may provide the information. When
they determine that they do not accept the request, the processing
returns to step S11, and the processes are repeated until an
information-exchange request for which forming a network is
desirable is received from another vehicle.
[0102] When the surrounding vehicles determine in step S12 that
they accept the request of the vehicle which requested network
forming, they receive the current position of the request-source
vehicle, which is the reference position, and its moving direction,
sent from the request-source vehicle, and calculate the relative
positions of the surrounding vehicles in step S13. In this
calculation, as shown in FIG. 10, for example, rectangular cells
having almost the same width and length as usual vehicles are
generated around the request-source vehicle, and the positions of
the surrounding vehicles are found. Numbers are assigned in advance
to the rectangular cells such that number 1
[0103] is assigned to the rectangular cell positioned immediately
in front of the request-source vehicle in its moving direction,
numbers 2
[0104] are assigned to rectangular cells clockwise starting from
the rectangular cell next to the rectangular cell having number
3
[0105] at the right, number 4
[0106] is assigned to the rectangular cell positioned immediately
in front of the rectangular cell having number 5
[0107] and the other numbers are assigned in the same manner. All
vehicles understand the arrangement of the rectangular cells, and
the surrounding vehicles detect their positions by the numbers of
the rectangular cells. In the case shown in FIG. 10, vehicles which
can perform inter-vehicle communications are located at the
rectangular cells 6
[0108] Then, in step S14, the surrounding vehicle determine the
response time when the vehicles send responses to the
request-source vehicle, from the positions of the vehicles relative
to the reference position. For example, the vehicle positioned
almost at the rectangular cell 7
[0109] has already understood as described above that the vehicle
is positioned at the rectangular cell 8
[0110] and therefore, determines the response time specified in
advance corresponding to the position according to the
response-start-time signals (time signals indicating time intervals
from signal reception) sent from the request-source vehicle. The
vehicle positioned at the rectangular cell 9
[0111] understands from the response-start-time signals that the
request-source vehicle finishes sending the network-forming request
at time t2, and starts receiving responses at t3. Since it is
determined that a vehicle positioned at the rectangular cell 10
[0112] can send a signal at time t3, and the vehicle positioned at
the rectangular cell 11
[0113] can send a signal at time t4, a predetermined time interval
after time t3, the vehicle positioned at the rectangular cell
12
[0114] knows that it can send a signal at time t4. In the same way,
all the other surrounding vehicles can determine their own response
times.
[0115] Each of the surrounding vehicles determines in step S15
whether its own response time has come. When the response time has
not come, the process of step S15 is repeated. When the response
time has come, the vehicle sends its free ID. The free ID may be
determined in advance, or may be generated by a random number. It
needs to be identified by the other vehicles. These processes are
performed, and then the processing proceeds to step S3 of FIG.
2.
[0116] In step S3 of FIG. 2, the vehicle which requested network
forming performs the first-order-network size restriction
processing and the processing for deciding vehicles to be included
in the first-order network. FIG. 4 shows the detailed operation
thereof. In the case shown in FIG. 4, the request-source vehicle
receives responses from the surrounding vehicles in step S21. FIG.
9(b) shows the response signals sent from the surrounding vehicles.
They are free-ID signals sent in step S16 indicating that the
corresponding surrounding vehicles accepted the network-forming
request. Next, the request-source vehicle determines in step S22
whether it applies a restriction to the first-order network. More
specifically, the request-source vehicle determines whether
vehicles (to be included in the first-order network) which perform
direct communications with the request-source vehicle are
restricted to a predetermined number of vehicles. This
determination can be automatically performed by request information
which applies a restriction determined in advance, such as detour
request information which applies the above-described
restriction.
[0117] Then, the number of responding vehicles is counted in step
S23. The counting is performed during a period called response
receiving (counting the number of responses) in the case shown in
FIG. 9. In step S24, it is determined whether the number of
responding vehicles has reached a predetermined number. When the
number of responding vehicles does not reach the predetermined
number, the processing returns to step S21, and receiving responses
from surrounding vehicles and the subsequent processes are
repeated. When it is determined that the number of responding
vehicles has reached the predetermined number, response receiving
is stopped in step S25.
[0118] In the case shown in FIG. 9, the vehicle positioned at the
rectangular cell 13
[0119] makes a response after the vehicle positioned at the
rectangular cell 14
[0120] the vehicle positioned at the rectangular cell 15
[0121] does not make a response because it is not included in the
network, and the vehicle positioned at the rectangular cell 16
[0122] makes a response. In the case shown in FIG. 9, it has been
already determined that receiving responses is stopped when three
vehicles have responded. Therefore, when the request-source vehicle
receives the response from the vehicle positioned at the
rectangular cell 17
[0123] it is determined that the number of responding vehicles has
reached the predetermined number, and receiving responses is
stopped to restrict the network size as shown in FIG. 9.
Alternatively, the request-source vehicle may transmit a signal,
indicating that receiving responses have been stopped, to the
surrounding vehicles to prevent them from responding.
[0124] The vehicles to be included in the first-order network are
decided in step S26, and the processing returns to step S4 of FIG.
2. The request-source vehicle sends its genuine ID and a data
transmission request to the vehicles included in the first-order
network with the use of the genuine PN code. More specifically, the
request-source vehicle sends the genuine ID to the vehicles
included in the network at time t13 as shown in FIG. 9(a), and the
vehicles included in the network send their genuine IDs in the
order specified in advance at time t14, time t15, and time t16 by
the use of the genuine PN code as shown in FIG. 9(c), FIG. 9(d),
and FIG. 9(e).
[0125] With the above-described operation, communications become
possible between vehicles which did not know their IDs at first. In
addition, genuine IDs are not superfluously made available to third
parties, and are reported only to vehicles which need the genuine
IDs. Since the number of vehicles included in the first-order
network can be restricted, when it is preferred that information is
exchanged among vehicles positioned in a limited area, such as in
forming a network for a specific intersection or in forming
detour-information-exchange network, vehicles to be included in the
network can be restricted in advance, and when it is preferred that
information is obtained in a wide area, such as
surrounding-resort-facility information, the area can be extended.
Even when genuine IDs have not been known, communications with each
vehicle can be performed with the ID-exchange timing being shifted,
which prevents mutual interference caused by simultaneous responses
sent from many vehicles.
[0126] After the first-order-network restriction has been decided
as described above, when a vehicle included in the first-order
network is provided with a relay function for relaying signals sent
from vehicles included in a second-order network, the first-order
network can be connected to the second-order network. In the same
way, the first-order network can be connected to a third-order
network, a fourth-order network, etc., to form a very-wide-area
network. The network-forming-restriction decision processing shown
in step S6 of FIG. 2 is also applied to vehicles included in such a
very-wide-area network to restrict the network and to finally
decide an appropriate-area network.
[0127] The process of step S6 of FIG. 2 can be sequentially
operated according to an operation flow shown in FIG. 5. FIG. 5
shows a case in which three types of network-forming-restriction
processing are sequentially achieved. The order of these types of
processing can be specified in a desired manner. Each type of
processing is shown in FIG. 6 to FIG. 8. As shown in FIG. 5, in the
network-restriction-decision processing in step S6 of FIG. 2, it is
determined first in step S31 whether network-forming-restriction
processing is performed according to the number of times relay
processes are allowed. When it is determined that
network-forming-restriction processing is performed according to
the number of times relay processes are allowed in order to prevent
a too-wide extension of the network caused by a large number of
relay processes because information sent to the vehicles included
in the network needs to pass through many local networks, the
processing proceeds to step S32, and network-forming-restriction
processing is performed according to the number of times relay
processes are allowed, as described in detail in FIG. 6.
[0128] When it is determined in step S31 that it is not necessary
to perform network-forming-restriction processing according to the
number of times relay processes are allowed, or when it is
necessary to perform the restriction processing and the restriction
processing has been achieved, the
network-forming-restriction-decision processing proceeds to step
S33, and it is determined whether network-forming-restriction
processing is performed according to a predetermined-distance area.
When it is determined that information should be exchanged only
with vehicles positioned in a predetermined-distance area from a
specific point such as the center of balance or the center of the
network or a specific intersection, in order to prevent the input
of not-useful information relative to desired information, caused
by the vehicles included in the network being positioned too far
away, the network-forming-restriction-de- cision processing
proceeds to step S34, and network-forming-restriction processing is
performed according to a predetermined-distance area, as described
in detail in FIG. 7.
[0129] When it is determined in step S33 not to perform
network-forming-restriction processing according to a
predetermined-distance area, or when it is necessary to perform the
restriction processing and the restriction processing has been
achieved, the network-forming-restriction-decision processing
proceeds to step S35, and it is determined whether
network-forming-restriction processing is performed according to a
network-forming time period. When information is required by a
specific time, such as a case in which the vehicle wants to obtain
information about an event to be held at ten o'clock that day, by
around eight o'clock, the network-forming-restriction-decision
processing proceeds to step S36, and network-forming-restriction
processing is performed according to a network-forming time period,
as described in detail in FIG. 8.
[0130] When it is determined in step S35 not to perform
network-forming-restriction processing according to a
network-forming time period, or when the restriction processing has
been achieved in step S36, the network-forming-restriction-decision
processing proceeds to step S37, and the network is finally decided
in step S7 of FIG. 2.
[0131] As shown in FIG. 6, in the network-forming-restriction
processing based on the number of times relay processes are
allowed, performed in step S32 of FIG. 5, it is first determined in
step S41 whether the vehicle has recorded in its memory, or other
memory, previously specified numbers of times to restrict relay
processes. When it is determined that the vehicle has recorded
already specified number of times values, the vehicle selects in
step S42 the already specified number of times corresponding to the
type of information required in the network. For example, the
number of times relay processes are allowed is set to 30 in a
network which requires detour information, the number of times
relay processes are allowed is set to 50 in a network which
requires the traffic-jam information for an ordinary road, and the
number of times relay processes are allowed is set to 100 in a
network which exchanges sightseeing-guide information.
[0132] When it is determined in step S41 that the vehicle has not
recorded previously specified number of times values to restrict
the number of times relay processes are allowed, the user enters
the number of times relay processes are allowed according to the
type of network in step S45. After the user specifies the number of
times relay processes are allowed in this way, or it is
automatically specified, it is determined in step S43 in the case
shown in FIG. 6 whether the network-forming-request-sourc- e
vehicle uses this restriction processing. This determination can be
made by entering a selection into the inter-vehicle communication
unit in advance, and by reading the input.
[0133] When it is determined in step S43 that the
network-forming-request-- source vehicle performs the restriction
processing, the network-forming-request-source vehicle specifies
the termination of the process of receiving signals relayed the
predetermined number of times or more, in step S44. The termination
is recorded in the relay-count-restriction processing section 63 of
the network-forming-restriction-decision processing section 6 in
the inter-vehicle communication apparatus 1 shown in FIG. 1. When
the termination is recorded, and the network is decided, the
termination data can be read in subsequent information-exchange
processing to determine whether information is sent from a vehicle
positioned in a restricted area.
[0134] When it is determined in step S43 that the
network-forming-request-- source vehicle does not perform the
restriction processing, the network-forming-request-source vehicle
sends the already specified number of times relay processes are
allowed, selected in step S42 or the number of times relay
processes are allowed entered by the user in step S45, to the
vehicles included in the first-order network in step S46. When the
number of times relay processes are allowed is included in
network-forming data, the vehicles included in the first-order
network can read it to perform subsequent processing. Each of the
vehicles included in the first-order network specifies the
termination of a relay process of signals relayed the number of
times relay processes are allowed or more, in step S47. The
termination is recorded in the relay-count-restriction processing
section 86 of the relay-control processing section 8 shown in FIG.
1. When the termination is specified in the vehicles which perform
relay processes and the network is decided, this termination data
can be read in subsequent relay processes to determine whether a
signal is sent from a vehicle which is allowed to perform a relay
process. After the termination is specified, the network-forming
restriction processing goes to step S33 of FIG. 5, in step S48.
[0135] As a result of the termination specified in step S44,
superfluous information sent through relay processes which were
performed more than the specified number of times relay processes
are allowed is excluded in subsequent information-exchange
communications. As a result of the termination specified in step
S47, superfluous information is excluded in subsequent
information-exchange communications since each of the vehicles
included in the first-order network checks a signal to which
another vehicle asks to apply a relay process, and does not perform
a relay process if the signal is to be sent to the
network-forming-request-source vehicle through relay processes
which are performed more than the specified number of times relay
processes are allowed.
[0136] The restriction result obtained by such
network-forming-restriction processing according to the number of
times relay processes are allowed can, for example, be shown by
reference to FIG. 11. The local vehicle C1 forms a first-order
network (C1) in which the local vehicle C1 can perform direct
communications, and vehicles C2 and C3 included in the first-order
network also form networks C2 and C3 in which the vehicles C2 and
C3 can perform direction communications, respectively. Therefore,
the information of the vehicles C2 and C3 can be directly received
by the local vehicle without a relay process. Since a vehicle C4 is
positioned in the network (C2) of the vehicle C2 as the local
vehicle C1 is, the information of the vehicle C4 can be sent to the
local vehicle C1 by the relay process of the vehicle C2, and hence
the information of the vehicle C4 is relayed-once information.
[0137] In the same way, since a vehicle C5 is positioned in the
network (C3) of the vehicle C3 as the local vehicle C1 is, the
information of the vehicle C5 can be sent to the local vehicle C1
by the relay process of the vehicle C5, and hence the information
of the vehicle C5 is relayed-once information. In the same way, the
information of a vehicle C6 can be sent to the local vehicle C1 by
the relay processes of the vehicles C5 and C3, and hence the
information of the vehicle C6 is relayed-twice information. The
information of a vehicle C7 is relayed-three-times information.
[0138] When the local vehicle sets the number of times relay
processes are allowed to two, for example, the information of the
vehicle C7 can be restricted by the process of the local vehicle or
the process of the vehicle C3 included in the first-order network
(C1). In the restriction process of the local vehicle according to
the number of times relay processes are allowed, receiving is
disabled because the vehicle C7 is not included in the wide
network, or the information of the vehicle C7 is received by the
local vehicle but not processed. A vehicle relaying the
information, other than the vehicles included in the first-order
network can perform the restriction process. In addition, a vehicle
which attempts to send information can read restriction data
included in the network-forming data, obtain the required number of
times relay processes are used until information reaches the
network-forming-request-source vehicle, and stop transmission when
the required number of times is equal to or larger than a
predetermined number.
[0139] When a network-forming restriction such as that described
above is applied according to the number of times relay processes
are allowed, the optimum network area can be specified by
restricting the number of times relay processes are allowed to an
appropriate value, according to the type of a network, such as to
30 in a detour network, to 50 in an ordinary-road traffic-jam
network, and to 100 in a sightseeing-guide network. This prevents
traffic-jam information in Osaka from being sent to Tokyo.
Depending on the type of network, the restriction can be removed,
if necessary. Even when a group constituting a network is moved or
changed, if a component of the network exists, the network is
maintained. When a network cannot be maintained, it can be made
extinct.
[0140] Referring to FIG. 12, in the network-forming-restriction
processing performed according to a predetermined-distance area in
step S34 of FIG. 5, when a network for the local vehicle C11 is
formed, if vehicles C13, C14, and C15 are positioned in the
first-order network (C11) of the local vehicle C11, the vehicle C13
and a vehicle C16 form a network and therefore, the information of
the vehicle C16 can be sent to the local vehicle C11 through the
relay process of the vehicle C13, the information of a vehicle C12
can be sent to the local vehicle C11 through the relay process of
the vehicle C15 in the same way, and the information of a vehicle
C17 can be sent to the local vehicle C11 through the relay
processes of the vehicles C12 and C15. For example, the center of
balance of the network for the local vehicle C11 is obtained with
the positions and density of vehicles included in the network being
taken into account, or a point close to the local vehicle is set to
the center of the network, and the area a predetermined distance
from the center of balance of the network or the center of the
network is set to an effective area serving as the
predetermined-distance area.
[0141] In such restriction processing, as shown in FIG. 7, the
center of balance or the center of the vehicles to be included in
the network is specified first in step S51. A tentative
network-forming area larger than the area expected in advance is
first specified around the local vehicle, and the center of balance
can be obtained from the vehicle distribution in the tentative
network-forming area. The center of the network is basically set to
the local vehicle, but it can be set to any point such as a point a
predetermined distance ahead of the local vehicle in its moving
direction.
[0142] Then, it is determined in step S52 whether the local vehicle
has previously specified restriction distances based on the types
of networks by recording them in a memory or by other methods. When
it is determined that the local vehicle has the already specified
restriction distances, the local vehicle selects in step S53 the
already specified restriction distance based on the type of the
network. When it is determined in step S52 that the local vehicle
does not have already specified restriction distances based on the
types of networks, the user enters a restriction distance based on
the type of the network in step S56. The set restriction distance
can indicate the radius of a circle. Alternatively, it can indicate
the shorter radius or the longer radius of a predetermined-shape
ellipse in which the radius is increased from the shorter radius to
the longer radius at a predetermined rate. In this case, the
restriction distance can be set correspondingly to the moving
direction of the local vehicle.
[0143] Such a restriction distance can be specified according to
the type of network. Alternatively, it can be specified such that,
in a tentative network-forming area larger than the area expected
in advance, used to calculate the center of balance, the number of
vehicles included in the area specified by a distance from the
center of balance or the center of the network is obtained, and the
distance corresponding to the area in which the obtained number of
vehicles is appropriate is set to the restriction distance.
Specifying the number of vehicles substantially has the same
meaning as specifying the density of vehicles in the network.
Selecting both or either of the restriction distance based on the
number of vehicles or the density of vehicles and the restriction
distance based on the type of a network in order to form the
network can be specified in a desired manner.
[0144] Methods other than those described above for obtaining the
center of balance of a network or specifying the center of the
network can be used. When a network for driving safely at a
specific intersection is formed by vehicles positioned around the
intersection, for example, the intersection can be set to the
center of the network, and the size of the network can be specified
by a distance from the intersection. When a network related to the
road on which the local vehicle is currently moving is formed, the
network-forming area can be specified by a predetermined distance
from the local vehicle in its moving direction, a predetermined
distance from the local vehicle in the direction opposite the
moving direction, and a predetermined distance from the road in the
direction perpendicular to the road.
[0145] After the user specifies the restriction distance in this
way or it is automatically specified, it is determined in step S54
in the case shown in FIG. 7 whether the
network-forming-request-source vehicle uses this restriction
processing, in the same way as in step S43 of FIG. 6. This
determination can also be made by entering a selection into the
inter-vehicle communication unit in advance, and by reading the
input.
[0146] When it is determined in step S54 that the
network-forming-request-- source vehicle performs the restriction
processing, the network-forming-request-source vehicle specifies
the termination of the process of receiving signals sent from
outside the restriction-distance area in step S55. The termination
is recorded in the network-forming-distance-area-restriction
processing section 64 of the network-forming-restriction-decision
processing section 6 in the inter-vehicle communication apparatus 1
shown in FIG. 1.
[0147] When it is determined in step S54 that the
network-forming-request-- source vehicle does not perform the
restriction processing, the network-forming-request-source vehicle
sends the already specified restriction distance selected in step
S53 or the restriction distance entered by the user in step S56 to
the vehicles included in the first-order network in step S57. When
the center of balance or the center position, and the restriction
distance are included in network-forming data, the vehicles
included in the first-order network can read them to perform
subsequent processing. Each of the vehicles included in the
first-order network specifies the termination of a relay process of
signals sent from vehicles positioned outside the restriction
distance area, in step S58. The termination is recorded in the
network-forming-distance-area-restriction processing section 87 of
the relay-control processing section 8 shown in FIG. 1. After the
termination is specified, the network-forming restriction
processing goes to step S35 of FIG. 5, in step S59.
[0148] As a result of the termination specified in step S55,
superfluous information sent from vehicles positioned outside the
specified restriction distance is excluded in subsequent
information-exchange communications. As a result of the termination
specified in step S58, superfluous information is excluded in
subsequent information-exchange communications since each of the
vehicles included in the first-order network checks a signal to
which another vehicle asks to apply a relay process, and does not
perform a relay process if the signal was sent from a vehicle
outside the restriction distance. With such network-forming
restriction processing based on a restriction distance, vehicles
positioned within a predetermined-distance area from the center of
balance or the center can be included in a network as shown in FIG.
12.
[0149] The restriction process based on a restriction distance is
performed when the local vehicle does not receive information sent
from vehicles positioned outside the area of the vehicles included
in the network. In addition, the restriction process is performed
when the local vehicle receives signals but does not process a
signal received from vehicles positioned outside the area of the
vehicles included in the network. A vehicle relaying the
information, other than the vehicles included in the first-order
network can perform the restriction process. In addition, in the
same way as in the case of FIG. 6, when a vehicle which attempts to
send information has come to know according to the restriction
distance included in the network-forming information that the
vehicle is positioned outside the network area, the vehicle can
stop transmission.
[0150] When a network-forming restriction such as that described
above is applied according to a restriction distance, the optimum
network area can be specified by restricting the network to have an
appropriate size according to the type of network, or by
restricting the network to have an appropriate size according to
the number of vehicles or the vehicle density in the network, such
as by restricting a detour network to have a radius of 1 km, an
ordinary-road traffic-jam network to have a radius of 3 km, and a
sightseeing-guide network to have a radius of 20 km. Even when a
group constituting a network is moved or changed, if a component of
the network exists, the network is maintained. When a network
cannot be maintained, it can be made extinct.
[0151] As shown in FIG. 13, in the network-forming-restriction
processing performed according to a network-forming time period in
step S36 of FIG. 5, when a network for the local vehicle C21 is
formed, if vehicles C23, C24, and C25 are positioned in the
first-order network (C21) of the local vehicle C21, the vehicle C23
and a vehicle C26 form a network and therefore, the information of
the vehicle C26 can be sent to the local vehicle C21 through the
relay process of the vehicle C23, the information of a vehicle C22
can be sent to the local vehicle C21 through the relay process of
the vehicle C25 in the same way, and the information of a vehicle
C27 can be sent to the local vehicle C21 through the relay
processes of the vehicles C22 and C25, for example. A restriction
time such as two hours can be specified in advance from when
information is requested at network forming to generate a
time-elapse restriction range. When a predetermined time has
elapsed, information exchanges are disabled in the network.
[0152] In such restriction processing, as shown in FIG. 8, it is
determined in step S61 whether the local vehicle has previously
specified restriction periods based on the types of networks by
recording them in a memory or by other methods. When it is
determined that the local vehicle has the already specified
restriction periods, the local vehicle selects in step S62 the
already specified restriction period based on the type of network.
When it is determined in step S61 that the local vehicle does not
have already specified restriction periods based on the types of
networks, the user enters a restriction period based on the type of
the network in step S65.
[0153] After the user specifies the restriction period in this way
or it is automatically specified, it is determined in step S63 in
the case shown in FIG. 8 whether the network-forming-request-source
vehicle uses this restriction processing, in the same way as in
step S43 of FIG. 6 or in step S54 of FIG. 7. This determination can
also be made by entering a selection into the inter-vehicle
communication unit in advance, and by reading the input.
[0154] When it is determined in step S63 that the
network-forming-request-- source vehicle performs the restriction
processing, the network-forming-request-source vehicle specifies
the termination of the process of receiving signals which have
exceeded the restriction period in step S64. The termination is
recorded in the communication-time-restri- ction processing section
65 of the network-forming-restriction-decision processing section 6
in the inter-vehicle communication apparatus 1 shown in FIG. 1.
[0155] When it is determined in step S63 that the
network-forming-request-- source vehicle does not perform the
restriction processing, the network-forming-request-source vehicle
sends the already specified restriction period selected in step S62
or the restriction period entered by the user in step S65 to the
vehicles included in the first-order network in step S66. When the
restriction-period data is included in advance in network-forming
data, the vehicles included in the first-order network can read it
to perform subsequent processing. Each of the vehicles included in
the first-order network specifies the termination of a relay
process of signals which have exceeded the restriction period, in
step S67. The termination is recorded in the
communication-time-restricti- on processing section 88 of the
relay-control processing section 8 shown in FIG. 1. After the
termination is specified, the network-forming restriction
processing goes to step S37 of FIG. 5, that is, step S7 of FIG. 2,
in step S68.
[0156] As a result of the termination specified in step S64,
superfluous information sent with the specified restriction period
being exceeded is excluded in subsequent information-exchange
communications. As a result of the termination specified in step
S67, superfluous information is excluded in subsequent
information-exchange communications since each of the vehicles
included in the first-order network checks a signal to which
another vehicle asks to apply a relay process, and does not perform
a relay process if the signal reached with the restriction period
being exceeded. With such network-forming restriction processing
based on a restriction period, vehicles positioned in a
time-elapse-restriction range can be included in a network as shown
in FIG. 13.
[0157] The restriction process based on a restriction time period
is performed when the local vehicle does not receive information
sent with a predetermined period being exceeded. In addition, the
restriction process is performed when the local vehicle receives
signals but does not process a signal received with a predetermined
time period being exceeded. A vehicle relaying the information,
other than the vehicles included in the first-order network, can
perform the restriction process. In addition, when a vehicle which
attempts to send information has come to know according to the
restriction period included in the network-forming information that
the information to be sent exceeded the restriction period, the
vehicle can stop transmission. Further, the information search
section of the apparatus can be set such that it does not perform
searching for requested information which exceeds the restriction
period.
[0158] When a network-forming restriction such as that described
above is applied according to a restriction time period, the
optimum network area can be specified by restricting the
network-forming period to an appropriate period according to the
type of network, such as to 30 minutes in an ordinary-road
traffic-jam network, to half a day in a today's event information
network, and to 10 minutes in an emergency-vehicle information
network. Even when a group constituting a network is moved or
changed, if a component of the network exists, the network is
maintained. When a network cannot be maintained, or when the
restriction period has elapsed and the usefulness of the
information has run out, it can be made extinct.
* * * * *